Photoresist

ABSTRACT

Photocurable and solvent-developable compositions based on photopolymerizable (meth)acrylates, a photoinitiator for (meth)acrylates, an organic polymeric binder which comprises free carboxyl groups and has an acid number of at least 60, a blocked polyisocyanate crosslinking agent which has a cleavage temperature of at least 100° C., and an inert solvent in an amount such that the photocurable composition is pourable, are described.

The present invention relates to novel, developable photoresistcompositions which are suitable, in particular, as solder resists.

Solvent-free photocurable compositions based on compounds which can bepolymerized by means of free radicals and on blocked isocyanates aredisclosed in JP-A-54/132,633. These compositions are applied instructured form to a substrate and subsequently cured using UVradiation. They can be used, inter alia, as solder resists. Developablesystems are not described therein. Resists applied in structured fromgenerally have lower resolution than developable resists.

EP-A-115,354 discloses (meth)acrylate-based photoresists which containan aldehyde condensation resin precursor as crosslinking agent and aselected binder containing acid groups. These compositions have a longshelf life at room temperature and can be cured, on the other hand, attemperatures which are relatively low for resists of this type.

Photoresists are generally applied to a substrate by lamination or fromsolution. In these process steps, the resist is usually warmed, forexample during the lamination operation or during the evaporation of thesolvent after application from solution. Partial crosslinking generallytakes place even before the photostructuring. This can result in animpairment of the image quality, since partial crosslinking has occurredeven in the unexposed areas. It is thus a desirable property of thephotoresist that it undergoes as little chemical change as possible dueto this heat treatment. On the other hand, it is desirable that aphotoresist is cured rapidly and at the lowest possible temperaturesafter application and imagewise exposure in order that a high throughputin the apparatuses used with simultaneous saving of energy costs isachieved.

It has now been found that the known photocurable compositions can bemodified by using selected binders and crosslinking agents in a mannersuch that a developable photoresist is obtained which has a long shelflife, is simple to process from solution and using which high-resolutionimages can be achieved and which is distinguished by low brittleness andhigh heat and chemical resistance after thermal curing.

Compared with solder resists cured using hexamethoxymethylmelamine, theresists according to the invention are distinguished, surprisingly, byhigher latency. Thus, coatings of these resists can be applied even fromrelatively high-boiling solvents and subsequently dried quickly attemperatures of above 100° C. The number of solvents available forcoating is thus increased; in particular, non-halogenated solvents canbe employed. For certain coating methods, relatively high-boilingsolvents must be used, for example in curtain coating or screenprinting.

The present invention relates to a photocurable and solvent-developablecomposition comprising

a) a photopolymerizable acrylate or methacrylate,

b) a photoinitiator for component a),

c) a polymeric organic binder which comprises free carboxyl groups andhas an acid number of at least 60,

d) as crosslinking agent, a blocked polyisocyanate which has a cleavagetemperature of at least 100° C., and

e) an inert solvent in an amount such that the photocurable compositionis pourable.

Components a) to e) can each be in the form of individual compounds.However, it is also possible to employ mixtures of several of thesecomponents, for example mixtures of several (meth)acrylates.

Component a) may be a monomeric or oligomeric (meth)acrylate, so long asit is photopolymerizable, i.e. can be converted into crosslinked andinsoluble products, in particular by UV and/or VIS radiation.

These are, in particular, compounds comprising two or more functionalgroups of the formula I ##STR1## in which R₁ is hydrogen or methyl, X is--NR₂ -- and in particular --O--, and R₂ is hydrogen or C₁ -C₈ alkyl.

Compounds comprising groups of the formula I are generally esters oramides based on aliphatic, cycloaliphatic, aromatic or araliphaticpolyalcohols or polyamines.

Monomeric or oligomeric components a) are known per se to those skilledin the art of photoresists and are described, for example, inEP-A-115,354.

Preferred components a) are compounds of the formula II

    A--R.sub.3 --(A).sub.n                                     (II)

in which A is a radical of the formula I, n is 2,3 or 4, and R₃ is theradical of an aliphatic or cycloaliphatic n-hydric alcohol after removalof the functional groups.

Examples of radicals R₂ are ethyl, n-propyl, isopropyl, n-butyl,sec-butyl, n-pentyl, n-hexyl, n-heptyl, n-octyl and, in particular,methyl.

Examples of aliphatic alcohols on which the radical R₃ is based arealkylenediols, such as 1,2-ethanediol, 1,2-propanediol, 1,3-propanediol,1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 1,8-octanediol,1,10-decanediol, 1,12-dodecanediol, di- or triethylene glycol,tripropylene glycol, 2,2-dimethylolpropane; or trihydric aliphaticalcohols, such as trimethylolethane, trimethylolpropane,polyoxyethylated trimethylolpropane or glycerol; or tetrahydricalcohols, such as pentaerythritol.

Examples of cycloaliphatic alcohols on which the radical R₃ is based are1,3- or 1,4-cyclohexanediol or 1,4-dimethylolcyclohexane.

In addition to the acrylate and/or methacrylate groups, particularlypreferred components a) comprise additional functional radicals whichare reactive to isocyanates, for example amino groups or, in particular,free carboxyl groups or alcohol groups. Examples of these are(meth)acrylates of the abovementioned polyalcohols, in which only someof the alcoholic radicals are esterified.

Photoinitiators b) which can be employed are all initiators customaryper se for free-radical polymerization.

Examples of suitable photoinitiators b) are aromatic carbonyl compounds,for example benzoin, benzoin alkyl ethers, such as the isopropyl orn-butyl ethers, α-substituted acetophenones, in particular benzilketals, such as benzil dimethyl ketal, or, in particular, α-halogenatedacetophenones, such as trichloromethyl p-tert-butylphenyl ketone, or, inparticular, α-amino-substituted acetophenones, such asdimethylaminomethyl phenyl ketone or morpholinomethyl phenyl ketone, or,in particular, dialkoxyacetophenones, such as diethoxyacetophenone, or,in particular, α-hydroxyacetophenones, such as 1-hydroxycyclohexylphenyl ketone; or benzophenones, such as benzophenone itself orbis(4-dimethylamino)benzophenone; or metallocene initiators, such astitanocene initiators, for examplebis(π-methylcyclopentadienyl)bis(σ-pentafluorophenyl)titanium(IV); or astannane in combination with a photoreducible dye, for exampletrimethylbenzylstannane in combination with Methylene Blue or BengalPink; or a quinone or a thioxanthone in combination with an aminecomprising at least one hydrogen atom on an α-C atom, such asanthraquinone, benzoquinone or thioxanthone in combination withbis(4-dimethylamino)benzophenone or triethanolamine; or a thioxanthone,for example an alkyl- or halogen-substituted thioxanthone, for example2-isopropylthioxanthone or 2-chlorothioxanthone; or acylphosphineoxides.

Component c) can be various organic polymeric binders comprising freecarboxyl groups, so long as they have an acid number of at least 60 andare thus soluble as such in a developer. To this end, the bindergenerally comprises lateral free carboxyl groups. Binders of this typeare generally derived from polymerizable, ethylenically unsaturatedmonomers comprising free carboxyl groups. Examples of such monomers areacrylic acid, methacrylic acid, maleic acid or itaconic acid. Thesebinders generally also comprise further comonomers without acidicgroups, for example the esters or amides of the abovementioned acids or1-alkenes or styrene.

The binders may also comprise free carboxyl groups and acrylate ormethacrylate groups in the same molecule. These include, for example,products of the reaction of an epoxy(meth)acrylate with carboxylicanhydrides. Epoxy(meth)acrylate is to be understood as meaning productof the reaction of epoxy compounds, preferably based on novolaks orunmodified or modified bisphenol A, with acrylic acid or methacrylicacid. These epoxy(meth)acrylates are then reacted with carboxylicanhydrides, for example tetrahydrophthalic anhydride, hexahydrophthalicanhydride, pyromellitic dianhydride or benzophenonetetracarboxylicdianhydride. Polymeric binders of this type are described inEP-A-292,219 and GB-A-2,175,908.

Examples of further binders comprising free carboxyl groups and acrylateor methacrylate groups in the same molecule are products of the reactionof styrene-maleic anhydride copolymers with hydroxy(meth)acrylates, forexample 2-hydroxyethyl (meth)acrylate or 3-hydroxypropyl (meth)acrylate.Polymeric binders of this type are described in EP-A-287,019.

The polymeric binder c) generally has a molecular weight of from about2000 to 500,000 (number average).

Preferred binders c) are those which are soluble in alkaline aqueoussolvents. Photoresists which can be developed in aqueous solution can beformulated using binders of this type. Such resists are particularlypreferred.

These particularly preferred binders c) include homopolymers based onacrylic acid, methacrylic acid, maleic acid or itaconic acid, copolymersbased on acrylic acid, methacrylic acid, maleic acid or itaconic acidand styrene or esters of these acids, in particular the alkyl estersthereof.

Some of the binders to be used according to the invention arecommercially available. Examples of these are polymers of the Carboset®and Scripset® type. Further suitable polymeric binders c) are describedin EP-A-115,354.

The crosslinking agent d) used is a blocked polyisocyanate which has acleavage temperature of at least 100° C., or a mixture ofpolyisocyanates of this type. In the context of this description, thisis to be understood as meaning a blocked polyisocyanate in which atleast half the isocyanate groups are re-liberated by deblocking at atemperature of 100° C. and are available for reaction with theisocyanate-reactive functional groups of the other components of thephotoresist.

The polyisocyanate on which the blocked component d) is based may be anyaliphatic, cycloaliphatic, aromatic or araliphatic compounds having atleast two, preferably two to four, isocyanate groups which may havefurther substituents which are inert to isocyanate groups, such as alkylor alkoxy groups or halogen atoms.

These include, for example, the following compounds:2,4-diisocyanatotoluene, and technical-grade mixtures thereof with2,6-diisocyanatotoluene, 2,6-diisocyanatotoluene,1,5-diisocyanatonaphthalene, 4,4'-diisocyanatodiphenylmethane andtechnical-grade mixtures of various diisocyanatodiphenylmethanes (forexample the 4,4'- and 2,4'-isomers), diisocyanato-m-xylylene,N,N'-di(4-methyl-3-isocyanotophenyl)urea, 1,6-diisocyanatohexane,3,5,5-trimethyl-1-isocyanatomethylcyclohexane (isophorone diisocyanate),trimethyl-1,6-diisocyanatohexane, 1-methyl-2,4-diisocyanatocyclohexane,dimeryl diisocyanate, triisocyanatotriphenylmethane and4,4'-diisocyanatodicyclohexylmethane.

These polyisocyanates may be blocked by various radicals. Examples ofsuitable blocking components are β-dicarbonyl compounds, such asmalonates, acetoacetates or 2,4-pentanedione, or hydroxamates,triazoles, imidazoles, imidazolides, tetrahydropyrimidines, lactams,oximes, hydroxyimides, such as N-succinimide, or phenols or thiophenols.

Component d) may also be a urethanized, carbodiimidated or dimerized ortrimerized polyisocyanate or other forms of polyisocyanates which areinactive below 100° C., so long as their cleavage temperature is above100° C. Examples of these are urethanized4,4'-diisocyanatodiphenylmethane, carbodiimidated4,4'-diisocyanatodiphenylmethane, the uretdione of2,4-diisocyanatotoluene, the trimer of diisocyanatotoluene,N,N',N"-tri(6-isocyanatohexyl)biuret, 2,2,4-trimeric isophoronediisocyanate and trimeric hexane diisocyanates.

Preferred components d) have a cleavage temperature between 100° and160° C. Particularly preferred components d) are oxime-blockedpolyisocyanates, in particular diisocyanates.

The inert solvent e) must dissolve components a) to e) and is employedin an amount such that the photocurable composition is pourable. Thesolvent should not have an adverse effect on the shelf life of themixture and must therefore be substantially inert to the mixturecomponents. Furthermore, it should have the lowest evaporation pointpossible in order that it may easily be removed after application of thephotoresist to the substrate. Examples of suitable solvents arehydrocarbons, such as aliphatic hydrocarbons, for exampletrichloroethane; or aromatic hydrocarbons, such as dichlorobenzene; oresters, such as methyl glycol acetate, methoxypropyl acetate or ethyl3-ethoxypropionate; or ketones, such as diisopropyl ketone orcyclohexanone; or alcohols, such as methyl glycol or methoxypropanol; orlactones, such as γ-butyrolactone; or lactams, such asN-methylpyrrolidone.

The amount of the individual components of the compositions according tothe invention may be varied within broad limits depending on the natureand area of application of the radiation-sensitive mixture. Thefollowing weight data in each case relate to the total weight ofcomponents a) to e), unless otherwise stated.

The amount of polymerizable monomer or monomer mixture a) is generally1-50% by weight, preferably 10-30% by weight.

The amount of initiator component b) is generally 1-30% by weight, inparticular 5-20% by weight, based on the total weight of component a).

The amount of binder c) is generally 10-70% by weight, preferably 10-50%by weight.

The amount of crosslinking agent d) is generally 2-20% by weight,preferably 5-15% by weight.

The amount of solvent e) is generally 5-80% by weight, in particular15-60% by weight.

The compositions according to the invention may comprise furtheradditives which are customary per se, for example stabilizers,sensitizers, pigments, dyes, fillers, coupling agents, flow-controlagents, wetting agents and plasticizers. The amount of such additives isusually 0.01-50% by weight, based on the total composition.

The compositions according to the invention are highly suitable ascoating agents for substrates of all types, for example wood, textiles,paper, ceramics, glass, plastics, such as polyesters, polyolefins,cellulose acetate or epoxy resins, in particular glass fibre-reinforcedepoxy resins, and for metals, such as Al, Cu, Ni, Fe, Zn, Mg or Co, orfor semiconductor materials, such as Si, GaAs or Ge, or for insulatormaterials, such as Si₃ N₄ or SiO₂, in which an image or a protectivecoating is to be applied by exposure.

The invention also relates to a process for the production of reliefstructures comprising the steps:

i) application of the composition according to the invention to asubstrate surface,

ii) drying of the coated substrate by evaporation of the majority of thesolvent e), preferably by heating the coated substrate, so that thesolvent e) is substantially removed and a tack-free surface is produced,

iii) image-wise irradiation of the photosensitive coating with actinicradiation, so that the irradiated areas of the coating photopolymerizeand become less soluble than the non-irradiated areas of the coating,

iv) removal of the non-irradiated areas of the coating by treating thecoating with a solvent for the composition according to the invention,preferably with an alkaline aqueous developer,

v) heating the developed coating to temperatures above the cleavagetemperature of the blocked polyisocyanate d) in order to thoroughlycrosslink the irradiated composition.

The coated substrates can be produced, for example, by preparing asolution or suspension of the composition according to the invention.This is generally applied uniformly to a substrate by coating methodswhich are known per se. Examples of coating methods are spin coating,dipping, knife coating, curtain coating, brushing, spraying andreverse-roll coating.

The amount applied (coating thickness) and the type of substrate(coating base) depends on the desired area of application. It isparticularly advantageous that the compositions according to theinvention can be applied in thin coatings and are distinguished by goodresolution. If the radiation source and radiation-sensitive componentsare chosen appropriately, they are suitable for a broad range of areasof application where the production of structured images is desired.

However, their use is particularly advantageous in the production ofprinted circuit boards as photostructurable solder resist or aspermanent resist. These uses are likewise subject-matter of the presentinvention.

After the coating operation, the solvent is usually removed by drying,giving an amorphous coating of the resist on the base. The filmthicknesses after drying are preferably 5-150 μm. The drying is usuallycarried out at elevated temperatures, which are usually selected so thatno substantial deblocking of component d) takes place. The solvent canalso be removed by applying a vacuum.

The radiation-sensitive coating is subsequently exposed in a mannerknown per se to radiation in order to photopolymerize component a). Thisis generally carried out image-wise. As a consequence ofphotopolymerization of component a), the solubility is reduced at theexposed areas of the coating compared with the unexposed areas, so thatdifferentiation of the surface becomes possible.

The compositions according to the invention are exposed using actinicradiation. This is generally UV and/or VIS radiation. Radiation in therange from about 220-450 nm is preferred. Irradiation can be effectedusing all radiation sources which are known per se, for example mercuryhigh-pressure lamps or UV/VIS lasers. The process parameters, forexample irradiation duration and separation of radiation source andphotosensitive coating, will generally depend on the nature of theradiation-sensitive composition and on the desired properties of thecoating and can be established by those skilled in the art on the basisof routine experiments. The image-wise exposure can take place through aphotomask or by direct writing of a laser beam on the photosensitivecoating.

The exposure is followed by a development step. The action of adeveloper removes the unexposed areas of the photoresist. Virtually anysolvent for the unexposed composition in which the irradiated andpartially cured composition is insoluble or only partially soluble issuitable as developer.

Alkaline aqueous solutions are preferred as developers. These include,in particular, solutions of alkali metal carbonates, hydroxides,silicates and phosphates. These solutions may also comprise relativelysmall amounts of wetting agents and/or organic solvents.

Aqueous solutions of alkali metal carbonates, for example 1% sodiumcarbonate solution, are particularly preferred.

Development using organic solvents is likewise possible. Examples ofsuitable solvents are ketones, such as cyclohexanone, acetone or methylethyl ketone, or alcohols, such as 2-ethoxyethanol, diacetone alcohol ordiethylene glycol monobutyl ether.

After exposure and development, the coating is subjected to thermalaftertreatment. To this end, the coating is heated to temperatures suchthat the crosslinking agent d) is deblocked and the liberated isocyanategroups react with the carboxyl groups of the binder c) and, if present,with further isocyanate-reactive radicals of component a). Thetemperature in this step must be above the cleavage temperature of theblocked polyisocyanate and is chosen depending on the component d)employed. In each case, the temperature in this step is greater than100° C., preferably 120°-180° C.

I. SYNTHESIS OF THE PHOTORESIST BINDER POLYMER

Example 1: 54.51 g (0.1125 mol) of the product of the reaction ofbisphenol A diglycidyl ether with acrylic acid are dissolved in 131.7 gof dioxane. 0.87 g of di-tertiary-butyl-para-cresol and 32.2 g (0.1 mol)of benzophenonetetracarboxylic dianhydride are added to this solution at70° C. When the reaction mixture has come to the boil, 246 mg (2 mmol)of 4-dimethylaminopyridine are added as catalyst. After the mixture hasbeen refluxed for 26 hours, 2.25 equivlents of acid are found per kg ofreaction product, and the reaction is terminated.

Example 2: 54.51 g (0.1125 mol) of the product of the reaction ofbisphenol A diglycidyl ether with acrylic acid are dissolved in 114 g ofdioxane. 0.87 g of di-tertiary-butyl-para-cresol and 21.81 g (0.1 mol)of pyromellitic dianhydride are added to this solution at 70° C. Whenthe reaction mixture has come to the boil, 246 mg (2 mmol) of4-dimethylaminopyridine are added as catalyst. After the mixture hasbeen refluxed for 24 hours, 2.55 equivalents of acid are found per kg ofreaction product, and the reaction is terminated.

Example 3: 87.7 g of the product of the reaction of an advancedbisphenol A diglycidyl ether (softening point 70°-80° C.) with acrylicacid, 45.6 g of tetrahydrophthalic anhydride and 0.12 g of hydroquinoneare dissolved at room temperature in 180 ml of dioxane. 0.18 g of4-dimethylaminopyridine are added, and the mixture is refluxed for 24hours. The polymer is precipitated from water and dried. The yield is100%.

Example 4: 230 g of an epoxycresol novolak (epoxide value 4.35 eq./kg),64.7 g of acrylic acid, 0.59 g of di-tertiary-butyl-para-cresol and 1.47g of benzyldimethylamine are heated for 3.5 hours at 110° C. in 300 g ofethyl glycol acetate. During this time, the epoxide value drops to 0.3eq./kg. 131.8 g of hexahydrophthalic anhydride and 1.05 g of4-dimethylaminopyridine are subsequently added, and the mixture isboiled at 110° C. for a further 24 hours. 3.2 equivalents of acid arefound per kg.

II. PREPARATION AND PROPERTIES OF THE PHOTORESIST

Example 5: A solution comprising 9.2 g of Scripset® 550 (partiallyesterified copolymer based on styrene and maleic acid, from Monsanto),7.9 g of Scripset®540 (partially esterified copolymer based on styreneand maleic acid, from Monsanto), 3.0 g of tetraethylene glycoldimethacrylate, 2.0 g of trimethylolpropane triacrylate, 8.4 g ofUltramix talc (Cyprus), 0.21 g of dye (Orasol Blue GN; CIBA-GEIGY), 3.2g of pentaerythritol triacrylate, 1.5 g of2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 4.8 g ofbutan-2-one O,O'-[methylenebis(1,4-phenyleneiminocarbonyl)]dioxime, and0.2 g of 4,4'-bis(diethylamino)benzophenone in 53.2 g of cyclohexanoneis applied to a printed circuit board using a knife coater. The film issubsequently dried at 100° C. for 5 minutes. The coating obtained inthis way is exposed through a mask for 15 seconds using a mercuryhigh-pressure lamp (distance from sample bench: 50 cm). The exposedsample is developed in a 1% aqueous sodium carbonate solution and curedfor one hour at 140° C. A coating having good solder bath resistance (1minute at 270° C.) and a methylene chloride resistance of greater than30 minutes is obtained.

Example 6: A solution comprising 45.6 g of the solution from Example 1(18.3 g of solid), 8.8 g of a mixture of various acrylates (3.2 g oftetraethylene glycol dimethacrylate, 2.2 g of trimethylolpropanetriacrylate and 3.4 g of pentaerythritol triacylate), 9 g of Ultramixtalc (Cyprus), 0.21 g of dye (Orasol Blue GN; CIBA-GEIGY), 1.6 g of2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 4.8 g ofbutan-2-one O,O'-[methylenebis(1,4-phenyleneiminocarbonyl)]dioxime, 0.21g of 4,4'-bis(diethylamino)benzophenone and 0.2 g of FC-430 (3M Company)in 27.5 g of cyclohexanone is applied to a printed circuit board using aknife coater. The film is dried at 80° C. for 30 minutes, to give acoating thickness of approximately 40 μm. The coating obtained in thisway is exposed through a mask for 30 seconds using a mercuryhigh-pressure lamp (distance from the sample bench 50 cm). The exposedsample is developed in a 1% sodium carbonate solution in a spraydeveloper (Convac, spraying pressure 3-4 bar) for 75 seconds. Theexposed and developed board had a cross-hatch score of Gt0 (DIN 53151),and the pencil hardness is HB. Exposed and developed boards areadditionally cured for one hour at 140° C. The cross-hatch test givesGt0, pencil hardness 5 H, resistance in methylene chloride >1 h andsolder bath resistance>1 minute.

Example 7: A solution comprising 45.7 g of the solution from Example 2(18.3 g of solid), 8.8 g of a mixture of various acrylates (3.2 g oftetraethylene glycol dimethacrylate, 2.2 g of trimethylolpropanetriacrylate and 3.4 g of pentaerythritol triacrylate), 9 g of Ultramixtalc (Cyprus), 0.21 g of dye (Orasol Blue GN; CIBA-GEIGY), 1.6 g of2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 4.8 g ofbutan-2-one O,O'-[methylenebis(1,4-phenyleneiminocarbonyl)]dioxime, 0.21g of 4,4'-bis(diethylamino)benzophenone and 0.2 g of FC-430 (3M Company)in 27.4 g of cyclohexanone is applied to a printed circuit board using aknife coater. The film is dried at 80° C. for 30 minutes, to give acoating thickness of approximately 40 μm. The coating obtained in thisway is exposed through a mask for 60 seconds using a mercuryhigh-pressure lamp (distance from the sample bench 50 cm). The exposedsample is developed in a 1% sodium carbonate solution in a spraydeveloper (Convac, spraying pressure 3-4 bar) for 45 seconds. Theexposed and developed board had a cross-hatch score of Gt0 (DIN 53151),and the pencil hardness is HB. Exposed and developed boards areadditionally cured for one hour at 140° C. The cross-hatch test givesGt1, pencil hardness 7H, resistance in methylene chloride>1 h and solderbath resistance >1 minute.

Example 8: A solution comprising 18.3 g of the binder polymer fromExample 3, 8.8 g of a mixture of various acrylates (3.2 g oftetraethylene glycol dimethacrylate, 2.2 g of trimethylolpropanetriacrylate and 3.4 g of pentaerythritol triacrylate), 9 g of Ultramixtalc, 0.21 g of dye (Orasol Blue GN; CIBA-GEIGY), 1.6 g of2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 4.8 g ofbutan-2-one O,O'-[methylenebis(1,4-phenyleneiminocarbonyl)]dioxime, 0.21g of 4,4'-bis(diethylamino)benzophenone and 0.2 g of FC-430 (3M Company)in 27.5 g of cyclohexanone is applied to a printed circuit board using aknife coater. The film is dried at 80° C. for 15 minutes, to give acoating thickness of approximately 40 μm. The coating obtained in thisway is exposed through a mask for 15 seconds using a mercuryhigh-pressure lamp (distance from the sample bench 50 cm). The exposedsample is developed in a 1% sodium carbonate solution. The exposed anddeveloped board had a cross-hatch score of Gt0 (DIN 53151), and thepencil hardness is HB. Exposed and developed boards are additionallycured for one hour at 140° C. The cross-hatch test gives Gt0, pencilhardness 3H, resistance in methylene chloride>1 h and solder bathresistance>10 seconds.

Example 9: A solution comprising 22.6 g of the solution from Example 4(11.3 g of solid), 3.96 g of Scripset® 550 (partially esterifiedcopolymer based on styrene and maleic acid, from Monsanto), 3.96 g ofScripset® 540 (partially esterified copolymer based on styrene andmaleic acid, from Monsanto), 8.6 g of a mixture of various acrylates(2.3 g of tetraethylene glycol dimethacrylate, 2.1 g oftrimethylolpropane triacrylate, 2.5 g of pentaerythritol triacrylate and1.7 g of ethoxylated trimethylolpropane triacrylate), 7 g of Ultramixtalc, 0.21 g of dye (Orasol Blue GN; CIBA-GEIGY), 1.6 g of2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one, 7.0 g ofbutan-2-one O,O'-[methylenebis(1,4-phenyleneiminocarbonyl)]dioxime, 0.21g of 4,4'-bis(diethylamino)benzophenone and 0.2 g of FC-430 (3M Company)in 44.6 g of ethyl glycol ether acetate is applied to a printed circuitboard using a knife coater. The film is dried at 80° C. for 15 minutes,to give a coating thickness of approximately 30 μm. The coating obtainedin this way is exposed through a mask for 15 seconds using a mercuryhigh-pressure lamp (distance from the sample bench 50 cm). The exposedsample is developed in a 1% sodium carbonate solution. The exposed anddeveloped board had a cross-hatch score of Gt0 (DIN 53151), and thepencil hardness is HB. Exposed and developed boards are additionallycured for one hour at 140° C. The cross-hatch test gives Gt0, pencilhardness 3H, resistance in methylene chloride>1 h and solder bathresistance>1 minute.

What is claimed is:
 1. A photocurable and solvent-developablecomposition comprisinga) a photopolymerizable acrylate or methacrylate,b) a photoinitiator for component a), c) a polymeric organic binderwhich comprises free carboxyl groups and has an acid number of at least60, d) as crosslinking agent, a blocked polyisocyanate which has acleavage temperature of at least 100° C., and e) an inert solvent in anamount such that the photocurable composition is pourable.
 2. Acomposition according to claim 1, wherein component a) is a compound ofthe formula II

    A--R.sub.3 --(A).sub.n                                     (II)

in which n is 2, 3 or 4, R₃ is the radical of an aliphatic orcycloaliphatic n-hydric alcohol after removal of the OH groups, and A isa radical of the formula I ##STR2## in which R₁ is hydrogen or methyl,and X is -O-.
 3. A composition according to claim 1, wherein componenta) additionally comprises functional radicals which are reactive towardsisocyanates.
 4. The composition of claim 3, wherein said functionalradicals are free carboxyl or alcohol groups.
 5. A composition accordingto claim 1, wherein component b) is selected from the group consistingof benzoin, benzoin alkyl ethers, α-substituted acetophenones,benzophenones, titanocene initiators, stannanes in combination withphotoreducible dyes; quinones or thioxanthones in combination withamines which have at least one hydrogen atom on an α-C atom;thioxanthones and acylphosphine oxides.
 6. The composition of claim 5,wherein said α-substituted acetophenones are selected from the groupconsisting of α-halogenated-, α-amino-, dialkoxy-andα-hydroxyacetophenones.
 7. A composition according to claim 1 which canbe developed in alkaline aqueous media, wherein component c) is solublein an alkaline aqueous solvent.
 8. A composition according to claim 7wherein component c) is a homopolymer of acrylic acid, methacrylic acid,maleic acid or itaconic acid; orcomponent c) is a copolymer of acrylicacid, methacrylic acid, maleic acid or itaconic acid with styrene; orcomponent c) is a copolymer of acrylic acid, methacrylic acid, maleicacid or itaconic acid with an ester of acrylic acid, methacrylic acid,maleic acid or itaconic acid.
 9. A composition according to claim 1,wherein component c) is a polymeric organic binder comprising freecarboxyl groups and acrylic or methacrylic groups in the same molecule.10. A composition according to claim 1, wherein component d) is analiphatic, cycloaliphatic, aromatic or araliphatic di-, tri- ortetraisocyanate compound whose isocyanate groups are blocked byβ-dicarbonyl compounds, hydroxamates, triazoles, imidazoles,imidazolides, tetrahydropyrimidines, lactams, oximes, hydroxyimides,phenols or thiophenols.
 11. A composition according to claim 1, whereincomponent d) has a cleavage temperature between 100° and 160° C. and isan oxime-blocked polyisocyanate.